1. Field of the Invention
The present invention relates to a carriage drive unit for a printer, and in particular, to a carriage drive unit for a printer having, on a carriage, a typewheel and a printing hammer for striking the typewheel, and controlling transfer timing of the carriage in accordance with a strike of the printing hammer.
2. Prior Art
Prior to the present invention, in such a printer, transfer timing of a carriage is determined, when a printing hammer for striking a typewheel reaches a printing position, that is, an operation position where the printing hammer abuts a printing paper on a platen via a printing ribbon and a type element of a typewheel, by output of a drive control signal to a motor drive circuit for driving a carriage drive motor in order to transfer the carriage by a character to print the next character. Further, in such a printer, the difference of the impact force of the printing hammer in accordance with each area of characters brings about the difference of the reach time period Th in FIG. 6 which covers from the initial drive movement of the printing hammer until reaching the printing position.
Paying attention to the above point, Published Unexamined Patent Application No. sho 61-35976 discloses a printer which can determine the reach time period Th of a carriage to a printing position by associating the transfer timing thereof with each area of characters, that is, the difference of the impact force, and also shorten the stationary time of the carriage to increase a printing speed.
However, as shown in FIG. 6, even if a drive control signal SG2 is entered to drive a carriage drive motor at the same time when a printing hammer reaches the printing position from a waiting position in response to a drive control signal SG5 to drive the printing hammer, load and transmission loss of a drive force in a drive system for the carriage drive motor delay the starting of the carriage in the right direction by a constant time t1 after output of the drive control signal SG2. The response delay time period t1 prevents the printing speed from being increased.